In the course of providing healthcare to patients, it is necessary to monitor vital statistics and other patient parameters. A plurality of different patient monitoring devices are able to selectively monitor the electrical impulses generated by a patient via at least one electrode coupled to the skin of the patient at particular locations on the body of the patient. For example, the electrical activity of the heart is routinely monitored in clinical environments using an electrocardiogram (ECG) monitor. The ECG monitor is connected to the patient by a plurality of electrodes that monitor the electrical impulses of the patient's heart. From electrophysiological signals sensed by the electrodes connected to the patient, the ECG monitor is able to generate an ECG waveform that includes data representing a series of successive heartbeats. An exemplary ECG waveform representing a single heartbeat 2 sensed by the electrodes is depicted in FIG. 1. The waveform 2 is formed from a plurality of different types of waves representing different electrical activities during a normal heartbeat and plotted against an isoelectric line 3 representing a base voltage. The waveform is comprised of a P wave, a QRS complex, a T-wave and, in some instances, a U-wave. The P wave represents atrial depolarization and includes a maximum amplitude represented by a peak 4. The QRS complex represents rapid depolarization of the right and left ventricles. Prior to depolarization, the Q point falls below the isoelectric line 3 and forms a trough 5. During depolarization of the ventricles, the maximum amplitude of the R point is the peak 6 thereof. The amplitude of peak 6 of the R point in the QRS complex is much greater than the amplitude of the peak 4 of the P wave due to the higher muscle mass generally associated with the ventricles as compared to the muscle mass of the atria. Following the QRS complex is the T wave which represents the repolarization of the ventricles during recovery. The U wave, if present, is believed to represent the repolarization of the septum between the left and right ventricles and follows in time having a maximum amplitude less than a maximum amplitude of the T wave.
From the different types of waves and complexes that form an ECG waveform, various features of the ECG waveform have been used to identify and classify various types of heartbeats for clinical use in diagnosing a medical condition of the patient. Common characteristics (or features) of ECG waveforms include any of the presence or absence of individual types of waves or complexes, the PR interval, the PR segment, the ST segment and the ST interval. Additionally, characteristics between successive heartbeats such as the RR interval representing a distance between successive R points have been used to detect certain cardiac conditions. A commonly detected cardiac condition is atrial fibrillation (AFIB). AFIB is a supraventricular tachyarrhythmia characterized by uncoordinated atrial activation with consequent deterioration of atrial mechanical function. On the surface electrocardiogram, AFIB is described by the replacement of consistent P waves by rapid oscillations or fibrillatory waves that vary in size, shape, and timing, resulting in an irregular, frequently rapid ventricular response. The irregularity of the heart rate and absence of the normal P wave are important features in detecting AFIB from the ECG signals. It is therefore desirable to provide a system and method for improved P wave detection that can be used alone or in combination with other methods to detect various cardiac conditions. A system according to invention principles addresses deficiencies of known systems to improve cardiac condition detection.